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Image from www.nasa.gov Studies of Cyanoacetylene Oligomers: Cyano-Substituted Cyclobutadienes, Dewar-Benzenes, and Benzenes Jessica L. Menke Robert J.

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Presentation on theme: "Image from www.nasa.gov Studies of Cyanoacetylene Oligomers: Cyano-Substituted Cyclobutadienes, Dewar-Benzenes, and Benzenes Jessica L. Menke Robert J."— Presentation transcript:

1 Image from Studies of Cyanoacetylene Oligomers: Cyano-Substituted Cyclobutadienes, Dewar-Benzenes, and Benzenes Jessica L. Menke Robert J. McMahonUniversity of Wisconsin, Madison Henning HopfTechnische Universität Braunschweig, Braunschweig, Germany Jens-Uwe GrabowGottfried-Wilhelm-Leibniz-Universität, Hannover, Germany Midwest Astrochemistry Meeting University of Illinois November 8,

2 2 Herbst, E. J. Phys. Chem. A 2005, 109, 4017; Young, Y. L. Icarus 1987, 72, 468; Strobel, D. F. Int. Rev. Phys. Chem. 1983, 3, 145; Mizutani, H. Origins of Life 1975, 6, 513; Becker, R. S.; Hong, J. H. J. Phys. Chem. 1983, 87, 163; Herbst, E. Chem. Soc. Rev. 2001, 30, 168. Cyano-Containing Molecules in the ISM & Titans Atmosphere

3 3 Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl. 1989, 28, Hopf, H.; Witulski, B Pure & Appl. Chem. 1993, 65, 47. Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann. 1995, 613. Interesting/Unexpected Experimental Results

4 4 Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl. 1989, 28, Hopf, H.; Witulski, B Pure & Appl. Chem. 1993, 65, 47. Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann. 1995, 613. Proposed Reaction Pathway Relative energies (kcal/mol) computed using B3LYP/6-31G* level with ZPVE corrections Not seen experimentally

5 5 Guillemin, J. C.; Ferris, J. P. European Space Agency, [Special Publication], SP, 1992, ESA-SP Woods, P. M.; Millar, T. J.; Zijlstra, A. A.; Herbst, E. Astrophys. J. 2002, 574, L167. Photochemical Formation of Cyano-Benzenes

6 6 Rotational Constants (cm -1 ) Dipole Moment (D) Computed at the B3LYP/6-31G* level Computed Rotational Constants and Dipole Moments Rotational Constants (GHz) Wohlfart, K.; Schnell, M.; Grabow, J.-U.; Kupper, J. J. Mol. Spectrosc. 2008, 247, 119.

7 7 Isolation of Various Cyclobutadienes Isolated Cram, 1991 Isolated Masamune, 1977 Isolated Maier, 1988 Isolated Gompper, 1968 Matrix Isolated Peterson, 1997 Matrix Isolated Krantz, 1973 Self Destructive Molecule Lives Longer in Prison Image: Cram, D. J.; Cram, J. M. Container Molecules & Their Guests, Royal Soc. Of Chemistry: Great Britain, 1994, 209. Quote: Milgrom, L. J. Inclusion Phenom. Mol. Rcognit. Chem. 1992, 13, 97.

8 n = 0n = 1 n = 2 n = 3n = 4 Relative energies (kcal/mol) computed using B3LYP/6-31G* level without ZPVE corrections Maier, G.; Neudert, J.; Wolf, O.; Pappusch, D.; Sekiguchi, A.; Tanaka, M.; Matsuo, T. J. Am. Chem. Soc. 2002, 124, Balci, M.; McKee, M. L.; Schleyer, Paul von Rague J. Phys. Chem. A 2000, 104, Cyano-Substitution Effects on Cyclobutadiene Order of Stabilization tBu < H < CN < SiH 3 < Me < SiMe 3

9 9 Cyano-Substitution Effects on Cyclobutadiene Singlet-Triplet Gaps a S-T Gap < 0 = singlet ground state. b Corrected for ZPV energies. Singlet Triplet S-T gap

10 10 Current/Future Studies Krantz, A.; Lin, C. U.; Newton, M. D. J. Am. Chem. Soc. 1973, 95, Chapman, O. L.; De la Cruz, P.; Roth, R.; Pacansky, J. J. Am. Chem. Soc. 1973, 95, Bell,G. A.; Dunkin, I. R.; Shields, C. J. Spectrochin. Aceta, Part A, 1985, 41A, Webster, O. W. J. Am. Chem. Soc. 1966, 88, 4055.

11 Robert J. McMahon The McMahon Group – Nikki Burrmann – Katherine Traynor – Chris Shaffer – Laura Kopff – Brian Esselman – Alex Nolan – Matt Biller – Jeff Slosarxzyk – Dr. Caroline Pharr – Dr. Phillip Thomas NSF for funding Acknowledgements Lady Liberty on Lake Mendota, Lake Mendota, University of Wisconsin, Madison 11


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